The present invention relates to a communication terminal device, for example, a communication terminal device which is capable of receiving television (TV) broadcasting.
Conventionally, a method of setting a TV broadcasting frequency in a communication terminal capable of receiving TV broadcasting is proposed, for example, in JP-A-8-162909 which describes a control method and apparatus that involves acquiring positional information from information on a base station associated with a mobile telephone, and searching TV broadcasting frequencies previously registered in a communication terminal based on the positional information to set an appropriate TV broadcasting frequency to the communication terminal.
Another similar technique proposed, for example, in JP-A-7-111439, which discloses a receiver that can automatically select a broadcasting station, involves comparing information on a current geographical position acquired through the Global Positioning System (GPS) with an area in which a TV broadcasting is to be received, thereby determining a movement of a communication terminal between such areas, and automatically setting a TV television frequency suited to the receivable area of the current position.
However, the control method and apparatus described in JP-A-8-162909 must previously register a large number of base stations installed all over the country, positional information thereon, TV broadcast-ing frequencies, TV broadcasting receivable areas, and the like in correspondence to one another, and therefore fail to set an appropriate TV broadcasting frequency when a new base station is additionally installed or when an existing base station is removed from service. In addition, the control method and apparatus described in JP-A-8-162909 not only entail complicated operations for the registration but also require a large capacity of memories for storing such a huge amount of information, leading to difficulties in reducing the size and cost of the communication terminal. Further, since the huge amount of registered information must be searched for required information on an appropriate base station, positional information, TV broadcasting frequency, a TV broadcasting receivable area, and the like, TV broadcasting radiowaves cannot be normally received during the search, possibly causing fluctuations in a received video image which would interfere with TV watching. Particularly, when a mobile terminal roams among a plurality of receivable areas in which different TV broadcasting frequencies have been set, the image can fluctuate each time the communication terminal moves from one area to another.
The receiver described in JP-A-7-111439 in turn must continuously receive radiowaves from GPS satellites to monitor a current position at all times, and can therefore suffer from large power consumption and a reduced standby time. In addition, when the receiver is situated in an underground town or street or the like where radiowaves from the GPS satellites do not reach, the receiver cannot set a TV broadcasting frequency because of the inability to acquire positional information. Also, as is the case with JP-A-8-162909, the receiver is incapable of more promptly switching TV broadcasting frequency settings, it cannot normally receive TV broadcasting radiowaves during the switching, possibly causing fluctuations in a received video image which would interfere with TV watching.
It is therefore an object of the present invention to provide communication terminal devices which are capable of solving the problems discussed above to improve the usability thereof.